Well, thats no particular wonder. It turns out there are at least a dozen different aspects to it. Different products, sometimes originating from different companies, some free and included with the system, and some that cost extra.
From that article (which includes all the details), here is a quick cheat sheet:
Other posts: https://community.isc2.org/t5/forums/recentpostspage/user-id/1324864413
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